Chinese and foreign experts on Wednesday urged collectors to share the earliest and largest encyclopedia man has ever had -- the Great Encyclopedia of Yongle (Yongle Dadian) of the Ming Dynasty (1368-1644).

Yongle Dadian was the largest encyclopedia in China. Compiled between 1403 and 1407, it contains 22,877 volumes in 11,095 books. It is 12 times that of the famous encyclopedia compiled by the French author Diderot in the 18th century.

Much of Yongle Dadian was destroyed during foreign invasions. It is estimated only about 400 books remain in the world, being kept in eight countries and regions.

Soren Edgren, professor with the Princeton University in America, told a seminar in Beijing that "I think collectors in the world should return the Yongle Dadian to China. It belongs to China after all."

Edgren has also published an open letter on the subject via the Internet

David Helliwell, senior assistant librarian with the Oxford University in Britain, said, "It's China's literature. Beijing should have information about Chinese books no matter where they are and even if they can't have the books."

According to experts, the National Library of China houses 221 books of the Yongle Dadian. In the early 1950s, former Soviet Union returned 64 books to China and former East Germany three.

However, the American Library of Congress still has 41 books, the United Kingdom 51 and Germany five. The Yongle Dadian keepers also include Japan and the Republic of Korea.

"It is a tragedy and shame what we see today of the Yongle Dadian is only three to four percent of its original volume," said An Pingqiu, professor with the Peking University.

Ren Jiyu, director of the National Library of China, said, "Yongle Dadian is beyond comparison. If any person could offer their collection for the use of publishing and photocopying this treasure of mankind, he would be contributing to the research and international cultural communications, as well as being remembered as a hero for good."

The seminar attracted 90 experts from over 50 institutions in countries such as China, America and Japan.